1. Field of the Invention
The present invention relates to a digital camera for sensing the light from a subject so as to obtain a signal corresponding thereto, and particularly to control of power supply.
2. Description of the Prior Art
As a digital camera, in recent years, one has been known in which an image sensing unit is detachably attached to the camera body, interfaces for various apparatuses as accessories connect-able to the camera body are provided in addition to the image sensing unit, and not only shot images are recorded as image data but also its function can be extended by connecting an accessory to the camera body in accordance with the purpose. Digital cameras are becoming widespread, for example, as a peripheral apparatus of personal computers (PCs).
However, such conventional digital cameras are inconvenient to use and inferior in portability because in the digital cameras, the power source for driving circuits in an image sensing unit or an accessory is provided for each image sensing unit and each accessory and this increases the total number of necessary batteries. Moreover, although some digital cameras can be supplied with power from the commercial AC power source through an AC adapter when used indoors, even in such a case, the operability is inferior because it is necessary to unplug the AC adapter and plug another AC adapter every time the interface is changed.
To solve this problem, a digital camera has been proposed in which power is supplied to the circuits in the image sensing unit and an accessory connected to the camera body from the camera body by a power source provided in or connected to the camera body. In this case, since the power to be supplied varies among the circuits in the image sensing unit and accessories, a plurality of power source portions for supplying power suitable for each circuit from the power source are incorporated. Conventionally, since power is supplied to all the circuits, including the plurality of power source portions, in the camera body when the camera is activated, power consumption is great.